Yi-Tian Chang, Yuan Zhang, Yutong Zhang
Purpose Spindle cell and sclerosing rhabdomyosarcoma (sRMS/scRMS) are rare variants accounting for 5%–10% of all RMS cases. This study aimed to evaluate the feasibility of using drug sensitivity assay to guide real time treatment decisions in children with sRMS/scRMS. Methods We retrospectively analyzed 14 consecutive patients diagnosed with sRMS/scRMS between January 2020 and December 2024. All patients initially received two cycles of VAC (vincristine/dactinomycin/cyclophosphamide). If the tumor response is stable or progressive, subsequent treatment is tailored based on drug sensitivity assay. The primary endpoint was feasibility of drug sensitivity assay guided decision making. Secondary endpoints included objective response rate (ORR), PFS, and OS. Results Drug sensitivity assay revealed uniform platinum sensitivity across all patients. After two cycles of VAC, 13 of 14 patients exhibited either stable or progressive disease, suggesting limited efficacy of the VAC regimen in this cohort. These 13 patients were subsequently transitioned to a platinum containing regimen guided by drug sensitivity assay, following which an objective response was observed in all cases. The 5-year PFS and OS were 36.92% (95% CI, 11.82–61.33) and 53.85% (95% CI, 31.70–82.93), respectively. Compared with the historical median survival of 9 months for relapsed/refractory RMS, the outcomes in our cohort appeared to be somewhat longer, suggesting a potential clinical benefit. The approach proved to be feasible in all 14 patients. Conclusion Our findings suggest that drug sensitivity assay may represent a feasible and potentially useful tool for informing real time treatment decisions in children with sRMS/scRMS. The incorporation of such testing into the therapeutic algorithm for this chemotherapy resistant sarcoma variant may offer a means to individualize treatment and possibly improve prognostic outcomes. However, given the exploratory nature and limited sample size of this study, these observations should be interpreted with caution, and larger prospective studies are needed to confirm their validity.